Railway signal system



April 9, 1935. c. e. sun-s RAILWAY SIGNAL SYSTEM Filed Nov. 18, 1935 Inventor Chaunceg G-Suits,

His Attorneg- B-RELAY DROP-0117' VOL TA s:

Patented Apr. 9, 193 I j i I I UNITED STATES PATENT OFFICE RAILWAY SIGNAL SYSTEM Chauncey G. Suits, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application November 18, 1933, Serial No. 698,629

11 Claims. (01. 24634) My invention relates to railway signal systems tering the section the regulator regulates the and particularly to those of that type in which voltage to a different value than before. a signal is actuated in response to the passage of My invention will be better understood from a car or train along a portion of the railway track. the following description taken in connection 5 In certain common railway signal systems, a with the accompanying drawing, and its scope 6 voltage is applied across the rails of the track at will be pointed out in the appended claims. one end of an insulated section, termed a block, Referring to the drawing, Figs. 1 and 2 are cirand this voltage energizes a relay connected cuit diagrams showing the preferred and a modiacross the rails at the other end of the section. fled form of my invention; and Fig. 3 is a diagram The presence of a train in the section decreases showing relative Values o Various V a a ss 10 the resistance between the rails and the resulting the rails. decrease in voltage at the relay causes the relay In Fig. l of the drawing i represents a section to operate. It has always been a problem to suffior block of railway track comprising the rails 2 ciently reduce the resistance between the rails and 3 between the insulating joints 5 and 6. At

by the presence of a train to cause the operation one end of section i I have shown the relay 7 15 of the relay to be positive. This difiiculty has connected across the rails, which relay has back become more acute recently because of the decontacts 8 connected with any suitable signal velopment of light rolling stock, such as gas eleccircuit 9, it being understood that when there tric cars, and is particularly serious where rubber is no train in the section the relay is energized so tired vehicles are used. Where the operation of or pulled up as illustrated. At the other end of the relay depends upon the change in resistance the section I have shown means for applying a between the rails as in the present systems, a rectified voltage across the rails. This means diiiiculty occurs because the resistance between comprises the transformer ill whose primary conthe rails may change from two causes: first, the nects with the source of alternating current suppresence of a train in the section, and second, p1y which eXample ay be a 110 volt, 60 25 the change in leakage resistance between the cycle constant potential source, through the satrails. In practice both of these factors have a urable core reactor 52, which is provided with the total variation of the order of one hundred-fold. saturating winding 53. The secondary or trans- It is the object of my invention to provide an former I0 connects with the rails 2 and 3 through an improved system which avoids the diificulties of the full wave rectifier l4 and the limiting rethe present system and insures the proper operasister l5. Rectified current is supplied to the sattion of the signal relay notwithstanding wide vaurating winding l 3 of reactor l 2 from the source riations in the resistance between the rails due ll throug t a m It, the electron diseither to a train or to leakage. charge device ii, and the limiting resistor I8.

In accordance with my invention the operation .The electron discharge device i1 is shown as a 35 of the signal relay is dependent not only upon a tube having two similar anodes 2i? and 2! which change of resistance between the rails but upon connect with the opposite ends of the secondary the rate of change of that resistance, Thus my of transformer l6, and as having a cathode 23 proinvention difierentiates between the change in Vided With the heater The saturating Windresistance due to a train, which is Sudden, and ing l3 connects at one side through resistor I8 40 the change in resistance due to leakage, which is with the midpoint of the h of transform" relatively slow. To effect this result I provide er and at the other slde cohheqts with the means for regulating the voltage across the rails Cathode h h heater Connected which regulating means has a predetermined to be Supphed altetnahng curtellt from t g source ll through the limiting resistor 25. With time delay characteilstlc. The amount of delay this a T t1 d t d such that a substantially constant voltage is ppa a as r m e mural} supp 1e 1S a the source it to the saturating winding 13 in mammmedhcwss the mus m splte P changes In accordance with the temperature of the cathode leakage resistance but when a train enters the 23, it being understood that the reactance offered section producing asudden drop in resistance beby the reactor 12 is governed by the degree of 50 tween the rails sufficient time elapses before the t ti n f its core produced by the winding r u a m a becomes completely effective t0 [3 and as long as the temperature of the cathode restore the voltage to allow the r y to p 23 remains constant the reactance of reactor l2 Also I provide the regulator with means whereby also remains constant and a constant voltage is after the relay operates in response to atrain enapplied across the rails of the track if the re- 55 sistance between the rails does not change. In order that the voltage between the rails may be regulated for a substantially constant value, notwithstanding changes in resistance between the rails, I have provided the saturable core reactor 2'! which is connected in shunt with the cathode heater 24. Reactor 27 is provided with the saturating winding 28, which connects through the resistor :29 with the rails 2 and 3 whereby the reactance oflered by the reactor 21 and hence the current supplied to the cathode heater 24 varies in accordance with the voltage across the rails. Inasmuch as the temperature of the cathode 23 does not respond immediately to changes in the current supplied to the heater thereof but involves a certain time delay in responding to changes in heater current, it will be seen that with the above described apparatus changes in the voltage supplied to the'rails in response to changes in resistance across the rails, such as that due to a train entering the section, is made only after a definite time delay. This delay is suificient to enable the relay to operate before the voltage-between the rails is restored.

' Inasmuch as the signal relays commonly employed for'operation in'resp oinseto changes in traci; resistance have a pull-noel opening voltage somewhat higher than their drop-out or closing voltage, I have provided the regulator with means whereby after relay "5' operates to close the signal circuit in response to the presence of a train in the section, the voltage across the rails is regulated to a diiferent value. In the present case this new value is somewhat higher than before but is lower'than the pull-up or opening voltage of the relay. For this purpose the'relay isprovided withthe front contacts to which connect with opposite ends of the resistor 29 so that when there is no train in'the section and the relay is pulled up, the resistor is short circuited, and when the relay drops out due to a train entering the section the short circuitis opened. Since resistor 29 is'included in the saturation circuit of reactor 2? it will bes'een that thecathode 3 23 will operate at either one of two temperatures resulting in the application of either one of two voltages to the rails depending upon the position of the relay. Y'

The operation of the apparatus disclosed by Fig. 1 is as follows. "When there is no train in the section or block l, relay 1 is pulled up as represented in .Fig, l. "Whena train enters the section the resulting dew-ease in resistance between the rails causes a sudden decrease in voltage across the rails. This decrease in voltage is suff cient to cause the relay '5 to operate, that is, to drop out, whereby the back contacts 8 close the cucuit 9 and the front contacts. 38 are opened, Referring to Fig. 3, the regulated voltage when no train is in the block may be that shown at A while the relay dropout voltage represented byB m y be slightly lower than A. The aforementioned decrease in voltage across the rails to which is added the voltage drop now across resistor 29 causes a decrease in saturation of reactor 27. In accordance with the well known principles governing the operation of saturable core re ctors, this reactor now offers a greater impedance to the flow of cur-- rent therethrough' ands ince the reactor is in shunt with the heater 2 a greater current is supplied to. the heater. The resulting increase in temperature of the cathode 23 causes a greater electron flow between the cathode and the anodes 2,8, and 21 whereby. the saturation of re:

actor I2 is increased. The reactance offered by this reactor accordingly decreases, and hence the voltage applied across the rails increases. Because of the time required for the cathode 23 to change its temperature, the change in voltage applied tothe rails takes place only after a predetermined time delay, which time is suflicient for the relay 1 to operate. Relay 7 having operated and through its back contacts having opened the shunt circuit about resistor 29, the apparatus now regulates the voltage applied to the rails to a new and higher value, which value is somewhat below the relay pull-up-voltage. Referring again to Fig. 3 the new regulated voltage applied to the rails may be that represented at C, while the relay pull-up voltage may be that represented at 13. When the train leaves the section the resistance between the rails suddenly increases whence the relay is pulled up to open the signal circuit 3 and to close the shunt circuit about resistor .29. The apparatus now regulates h ta e spe led a r s he a s to the original lower value but this regulation is eifected only after a predetermined time delay governed by the time require d for the change in temperature of the hot cathode. Where the change in resistance between the rails takes place Slowly r xample, hee lfi fi tt the above described regulating means is sufiie Qciently rapid in its operation to preserve a sub? stantially constant voltage between the rails. It will be seen therefore, that the resistance between t a ma v r h ough wide ran eswithout operating the signal reiay'proyided these chan stalse place slowly. However, ii even a relatively small change in resistance between the rails takes place suddenly, as for example, when a car or train of relatively light construction enters the section, the relay will respond to give a signal.

In the modified form of my invention illustrated by Fig. 2, I suppl alternating current to the rails. from the source U through the limiting resistor 35, In this casethe voltage across the rails is controlled .by the saturable core reactor 36 Which, being connected across the rails, acts as a variable shunt, so that the volt age across the rails is that .of the supply .ll minus thev voltage drop across resistor '35 In this case the current supplied to the saturating i n 31 of rea to at is ha w i h Pa e the two-element electron discharge tube '38 v zhich not only controls the current value in the satu-v rating winding but also rectifies the current The tun a s abet ethqel 3. wmch i cluded in the series .nonelinear resonant Qil: cuit 46 comprising the self-saturating reactor and t e ca a tor 42- ,.h o f r l ar Is nant circuit is energized by thelsecondary of transformer 23 whose primary connects across the rails. Thesignal relay d4 is similar to relay 1 in Fig. 1 except that in addition to the back contacts 8 which control the signal circuit -'9 it includes a pair of front contacts 65 which connect circuit so with one end. ofhe secondary of transformer 43 and includes a second pairof rearcontacts, .5 which connect circuit All with an intermediate point i'lflof the samesecondary wind n The op ra i n f the modified form illustrated b g- 2 s a o owsthe e is. no tra n. in the section, the relay' is energized to. hold the; i a c r n t in lude. he whale o the e n ing; Q? i f @1 non-linear circuit til, as illustrated, The YQ'l-tr.

age applied to circuit 40 is such that the circuit is now in a resonant condition, hence the current supplied to the cathode 39 is a maximum and the current passing the tube 38 and the saturating winding 31 is a maximum. Reactor 36 accordingly being saturated ofiers a minimum impedance across the rails and the voltage across the rails therefore is a minimum which value may correspond to that represented at A in Fig. 3. When a train enters the section the resulting decrease in resistance between the rails causes the signal relay 44 to drop out and close the signal circuit 9. In so doing the relay changes the connections of the circuit 40 to include a fractional part only of the secondary of transformer 43. The decrease in voltage now applied to the non-linear resonant circuit 40 causes this circuit to become non-resonant, and the resulting decrease in current thereof allows the cathode 39 to become cooler. Less current therefore, is supplied to the saturating winding 31 and reactor 36 increases the impedance it offers to the shunt circuit across the rails, wherefor the voltage across the rails increases. This increase value may be that shown at C in Fig. 3. Because of the time required for the hot cathode 39 to change its temperature, the change in voltage between the rails takes place only after sufficient time has elapsed for relay 44 to operate. Since the relay has changed the connections of circuit 40 to include a portion only of the transformer secondary the apparatus now regulates the voltage between the rails to a diiferent or higher value than before. When the train leaves the section the resulting increase in voltage between the rails causes relay 44 to pick up and open the signal circuit 9 thus returning to its original position as illustrated. The circuit connections of the nonlinear resonant circuit 40 are now returned to their original form and the apparatus after a predetermined time interval again regulates the voltage between the rails to the original value which may be that shown at A in Fig. 3. As described in connection with Fig. l, a gradual change in resistance between the rails does not afiect the signal relay since the apparatus is able to regulate the voltage across the rails to preserve a substantially constant value.

While I have shown the various saturable core reactors described above as having a three-legged core structure, it will be understood that if desired each of these reactors may comprise two similar transformers connected as shown for example in my Patent 1,885,155 of November 1, 1932.

I have chosen the particular embodiments described above as illustrative of my invention and it will be apparent that various other modifications may be made without departing from the spirit and scope of my invention which modifications I aim to cover by the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:-

1. A railway signal system comprising means for applying a voltage across the rails of a track, an electromagnetic relay connected to be responsive to the voltage across said rails and a delayed action regulating means for restoring the voltage across the rails in response to a sudden decrease in resistance therebetween, the delay in action of said regulating means being suflicient to enable the relay to operate.

2. A railway signal system comprising means for applying a voltage across the rails of a track, a signal relay connected to be responsive to the voltage across said rails and means for regulating the voltage applied to the rails with a predetermined time delay, said means being constructed to regulate the voltage to a different value in response to the operation of said relay.

3. A railway signal system comprising means for applying a voltage across the rails of a track, time delay regulating means for regulating the voltage applied to the rails, a relay connected across said rails and m ans responsive to an operation of said relay for causing the regulating means to regulate to a higher value.

4. A railway signal system comprising means for applying a voltage across the rails of a track, means for regulating the voltage applied across the rails after a predetermined time delay, a relay connected across said rails and means responsive to the operation of said relay for causing the regulating means to regulate the voltage to a new value, said value being higher than the previous value but lower than the value at which said relay operates.

5. A railway signal system comprising means for applying a voltage across the rails of a track, means responsive to a decrease in resistance across the rails for regulating the applied voltage after a predetermined time delay, a relay connected across said rails and having contacts for controlling a signal circuit and having other contacts, and means connected with said other contacts for causing the regulating means to regulate the applied voltage to higher value.

6. A railway signal system comprising means for applying a voltage across the rails of a track, a relay connected across said rails and constructed to operate in response to a sudden drop in voltage across the rails, regulating means responsive to the operation of the relay for restoring said voltage and means controlled by said relay for causing the regulating means to regulate the voltage to a higher value.

7. A railway signal system comprising means for applying a voltage across the rails of a track, regulating means therefor including an electron discharge device having a hot cathode whose temperature controls the rate of regulation, means responsive to the voltage across the rails for causing the regulating means to regulate to produce either one of two different voltages and a relay connected across said rails for determining for which voltage the regulating means shall operate.

8. A railway signal system comprising means including a series reactor for supplying a regulated voltage across the rails of a track, an electron discharge device having a hot cathode arranged to control the reactance or" said reactor, means for supplying current to heat said cathode, a reactor controlled by the voltage across said rails for varying said current, a signal relay connected across said rails and means controlled by said relay for changing the current supply to said cathode.

9. A railway signal system comprising means for applying voltage across the rails of a track, a signal relay connected to operate in response to a decrease in voltage across the rails and means responsive to the operation or" said relay for restoring the voltage across the rails.

10. A railway signal system comprising means for applying voltage across the rails of a track, a signal relay connected to operate in response to a decrease in voltage across the rails and means responsive to the operation of said relay for raising the voltage across the rails to a value higher than the original value thereof.

1-1. A railway signal system comprising means for applying a, voltage across the rails of a track at one pOrtion thereof, a relay connected to operate in response to a decrease in voltage across said 5 rails of the track at another portion thereof and means responsive to a, slow decrease in resistance between the rails for maintaining a substantially constant voltage therebetween at said other portion and responsive to the'operation of said relay for producing an increase in voltage across the rails. m '7 CI-IAUNCEY G. SUITS. 

